"If you're mining on the coast, sooner or later you'll find a wreck," archaeologist Dieter Noli said in an interview Thursday.

Namdeb Diamond Corp., a joint venture of the government of Namibia and De Beers, first reported the April 1 find in a statement Wednesday and planned a news conference in the Namibian capital next week.

Judging from the notables depicted on the hoard of Spanish and Portuguese coins, and the type of cannons and navigational equipment, the ship went down in the late 1400s or early 1500s, around the time Vasco de Gama and Christopher Columbus were plying the waters of the New World.

"Based on the goods they were carrying, it's almost certain that it dates from that time," said John Broadwater, chief archaeologist at the U.S. National Oceanic and Atmospheric Administration.

"This find is very exciting because very few vessels from that period have been discovered," he said, adding that many early ships were thought to have wrecked in that area.

It was, Noli said, "a period when Africa was just being opened up, when the whole world was being opened up."

Not Diamonds But Other Treasure

In its search for diamonds, the company had originally cleared and drained a stretch of seabed, building an earthen wall to keep the water out so geologists could work.

Noli said one of the geologists saw a few ingots but had no idea what they were. Then the team found what looked like cannon barrels.

The geologists stopped searching for diamonds and sent photos to Noli, who had done research in the Namibian desert and has advised De Beers on the archaeological impact of its operations in the country.